NSX logs show either or both of the following:
2020-04-26 08:23:42.909 GMT ERROR TaskFrameworkExecutor-11 VdnCdoModeTask:153 - - [nsxv@6876 comp="nsx-manager" subcomp="manager"] Exception encountered in VDS dvs-xxxx
com.vmware.vshield.vsm.vdn.exceptions.XvsException: null
or
2020-04-26 08:24:42.812 GMT ERROR TaskFrameworkExecutor-26 Worker:219 - - [nsxv@6876 comp="nsx-manager" subcomp="manager"] BaseException thrown while executing task instance taskinstance-2014451
com.vmware.vshield.vsm.vdn.exceptions.XvsException: null
at com.vmware.vshield.vsm.vdn.service.task.VdnCdoModeTask.run(VdnCdoModeTask.java:120) ~[vsphere-1.0.jar:?]
at com.vmware.vshield.vsm.task.service.Worker.runtask(Worker.java:184) [vsm-core-1.0.jar:?]
at com.vmware.vshield.vsm.task.service.Worker.executeAsync(Worker.java:122) [vsm-core-1.0.jar:?]
at com.vmware.vshield.vsm.task.service.Worker.run(Worker.java:99) [vsm-core-1.0.jar:?]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_161]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_161]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_161]
Confirm that all hosts prepared for NSX are in a healthy, responsive, and connected state.
Also, review host preparation and ensure all communication channels are up.